/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.objcoding.calcite.csv.translate;

import com.google.common.collect.ImmutableMap;
import org.apache.calcite.schema.Table;
import org.apache.calcite.schema.impl.AbstractSchema;
import org.apache.calcite.util.Source;
import org.apache.calcite.util.Sources;

import java.io.File;
import java.util.Map;

/**
 * Schema mapped onto a directory of CSV files. Each table in the schema
 * is a CSV file in that directory.
 */
public class CsvSchema extends AbstractSchema {
    private final File directoryFile;
    private final CsvTable.Flavor flavor;
    private Map<String, Table> tableMap;

    /**
     * Creates a CSV schema.
     *
     * @param directoryFile Directory that holds {@code .csv} files
     * @param flavor        Whether to instantiate flavor tables that undergo
     *                      query optimization
     */
    public CsvSchema(File directoryFile, CsvTable.Flavor flavor) {
        super();
        this.directoryFile = directoryFile;
        this.flavor = flavor;
    }

    /**
     * Looks for a suffix on a string and returns
     * either the string with the suffix removed
     * or the original string.
     */
    private static String trim(String s, String suffix) {
        String trimmed = trimOrNull(s, suffix);
        return trimmed != null ? trimmed : s;
    }

    /**
     * Looks for a suffix on a string and returns
     * either the string with the suffix removed
     * or null.
     */
    private static String trimOrNull(String s, String suffix) {
        return s.endsWith(suffix)
            ? s.substring(0, s.length() - suffix.length())
            : null;
    }

    @Override
    protected Map<String, Table> getTableMap() {
        if (tableMap == null) {
            tableMap = createTableMap();
        }
        return tableMap;
    }

    private Map<String, Table> createTableMap() {
        // Look for files in the directory ending in ".csv", ".csv.gz", ".json",
        // ".json.gz".
        final Source baseSource = Sources.of(directoryFile);
        File[] files = directoryFile.listFiles((dir, name) -> {
            final String nameSansGz = trim(name, ".gz");
            return nameSansGz.endsWith(".csv")
                || nameSansGz.endsWith(".json");
        });
        if (files == null) {
            System.out.println("directory " + directoryFile + " not found");
            files = new File[0];
        }
        // Build a map from table name to table; each file becomes a table.
        final ImmutableMap.Builder<String, Table> builder = ImmutableMap.builder();
        for (File file : files) {
            Source source = Sources.of(file);
            Source sourceSansGz = source.trim(".gz");
//      final Source sourceSansJson = sourceSansGz.trimOrNull(".json");
//      if (sourceSansJson != null) {
//        final Table table = new JsonScannableTable(source);
//        builder.put(sourceSansJson.relative(baseSource).path(), table);
//      }
            final Source sourceSansCsv = sourceSansGz.trimOrNull(".csv");
            if (sourceSansCsv != null) {
                final Table table = createTable(source);
                builder.put(sourceSansCsv.relative(baseSource).path(), table);
            }
        }
        return builder.build();
    }

    /**
     * Creates different sub-type of table based on the "flavor" attribute.
     */
    private Table createTable(Source source) {
        switch (flavor) {
            case TRANSLATABLE:
                return new CsvTranslatableTable(source, null);
            default:
                throw new AssertionError("Unknown flavor " + this.flavor);
        }
    }
}
